Telephone system



Aug. 13, 1940.

Sheets-Sheet l RUDOLPH INVENTOR ANK STEHLIK ATTORNEY Filed Oct. 19, 1938 3 Sheets-Sheet 2 hbi INVENTOR RUDOLPH FRANK STEHLIK ATTORNEY Aug. 13, 1940- R. F. STEHLIK 3 TELEPHONE SYSTEM Filed Oct. 19, 1938 Z5 Sheets-Sheet 3 INVENTOR RUDOLPH FRANK STEHLIK ATTORNEY Patented Aug. 13, 1940 STATE TNT signor to Associated Telephone and Telegraph Company, Chicago, 111., a corporation of Dela.-

ware

Application ()ctober 19, 1938, Serial No. 235,719

In Great Britain November 3, 1937 11 Claims.

The present invention concerns improvements in or relating to automatic or semi-automatic telephone systems and has for its object the provision of arrangements whereby a series of impulses already used for setting up a connection may at the same time be stored and repeated for any required purpose.

According to the invention a mechanical impulse repeater is taken into use on the initiation of a call and is adapted to respond to impulses dialled by the subscriber at the same time as such impulses are controlling the setting up of a connection. When'the call has reached a certain stage it can be determined whether the mechani cal impulse repeater will be required and also Whether it will be required to transmit some or all of the digits registered. With a mechanical impulse repeater of the kind described in the J. W. McClew and C. R. Woodland British Patent 458,095 granted March 4, 1937, it will be necessary to suppress those impulses which are not required as the mechanism must be allowed to move to an extent corresponding to such impulse.

The invention is applicable to alternative routing and zone metering arrangements in which metering impulses are transmitted from relay equipment associated with an outgoing junction line and also for making a record of the called partys number, for instance, in recording by printing or punching on a tape or ticket the number of the .called party for the purpose of assessing the charge to be made to the calling party.

The invention will be better understood from the following description taken in conjunction with the accompanying drawings comprising Figs. 1 2 and 3 which show the invention as applied to an arrangement for alternative routing.

In the drawings Fig. 1 shows a trunking diagram for three exchanges A, B and C While Figs. 2 and 3 show the circuits of the selector repeater and mechanical impulse repeater located at exchange A. Referring to Fig. l in exchange A the finder switches F are permanently connected with selector repeaters SR and the seizure of a selector repeater is effective automatically to take into use a mechanical impulse repeater MIR. with its associated group of control relays. Local calls are set up over certain of the first 8 levels of the selector repeater and 2nd group selectors are accessibleover these levels. The 9th level is employed for setting up calls to exchange C and the 10th level for setting up calls to exchange B and in the present case it is assumed that the first 5 contacts in the 10th level have access to exchange B over direct junctions DJ and incoming selector 182. The remaining 5 contacts have access to exchange B via exchange 0 over the incoming selector IS at exchange C over the incoming selector IS at exchange 0 and the incoming selector Isl at exchange B. I

In the operation of the system a call from exchange A to exchange B will normally be set up over one of the direct junctions DJ, these junctions forming the preferred route. If however all the junctions are busy the connection is set up over the alternative route via exchange C.

It will be understood that if the connection is set up over the alternative route one more digit must be transmitted than if the call proceeds over the preferred route in order to effect the setting of the incoming selector IS at exchange C. The circuits of Fig. 2 shown an arrangement whereby this is possible.

Referring now to Figs. 2 and 3 when the line finder finds the calling line, relay A will operate over the loop extended to the selector repeater and at contacts a! closes a circuit for relay B. In addition at contact a2 relay A. prepares the impulsing circuit for subsequent switches if the call is a local one. Relay B in operating at contact bl extends earth back to the line finder over the P conductor; at contact 222 closes the circuit of the polarising winding of the back bridge relay D; at contact b3 prepares the impulsing circult to the vertical magnet and to the mechanical impulse repeater, at contact he prepares a test and operating circuit for the rotary switch RS over which the mechanical impulse repeater is associated with the selector repeater and at contact b5 prepares an operating circuit for relay I-IB.

If the mechanical impulse repeater MIR, Fig. 3 is busy an earth potential will be present on the P Wiper of the rotary switch RS and hence the magnet of the rotary switch RS, Fig. 2, will be energised over the following self-interrupting circuit: earth at contact icl, armature 112 and front contacts, bank contact and wiper P of the rotary switch RS, contacts hail, M, 71116, interrupter contacts rsm, winding of magnet RSM to battery. The rotary switch is therefore stepped until an idle mechanical impulse repeater is found, the idle condition being indicated by the absence of potential on the P wiper. In this case relay I-IB operates in series with the magnet RSM over the circuit: earth, rotary 01f normal contacts NHL contact 125, winding of relay HB, interrupter contacts rsm winding of magnet RSM to battery. The magnet does not however operate in this case owing to the high resistance of relay I-IB. Relay H3 in operating at contacts hbl and 71.112

completes the impulsing circuit from the mechanical impulse repeater over the outgoing speaking conductors; at contact 71173 transmits dial tone to the calling subscriber by induction over a third winding of relay A; at contact hbfi completes the impulsing circuit to the mechanical impulse repeater; at contact 71125 places a shunt round contact hafi to provide a holding circuit for relay IB independent of relay HA: at contact 71123 completes a further point in the holding circuit for relay IB; at contact hb'l closes a point in the release circuit of the mechanical impulse repeater; at contact 11178 prepares a circuit for relay IC and at contact hb9 completes a point in its own holding circuit.

The calling subscriber now dials the required number and the impulses are repeated at contact al to the vertical magnet VM in the selector repeater and also the impulsing magnet R, Fig 3, in the mechanical impulse repeater. Vertical off-normal contacts now operate and at contact N I, Fig. 2, open the dial tone circuit; at contacts N2 prepare the circuit for relay E and at contacts N3 prepare a point in the circuit of release magnet Z. In addition relay C is energised on the receipt of the first impulse and remains energised for the whole of the impulse series. Relay C, at contact cl places a shunt across the energising winding of relay D; at contact 02 completes a circuit for relay E and at contact 03 completes the circuit for relay IC, Fig. 3. Relay IC upon energising at contact z'cl completes a circuit for relay IB; at contact 2'02 operates relay IP and at contact 2'03 operates the marking magnet M in the mechanical impulse repeater. The marking magnet M is thus maintained energised for the whole of the impulse series. Relay IB in operating at contact z'bl energises the polarising winding of relay DA; at contact 2'b2 closes a holding circuit for itself independent of contact icl; at contact 2723 shunts contact zs2 and at contact z'b l prepares a circuit for relay IS. Relay IP in operating at contact ipl extends earth to the back contact associated with the armature ib2 in order to provide an extra guard period for the repeater during release or if the subscriber should replace his receiver before the connection is completed; at contact z'pZ magnet CSM of the control switch CS is energised but this switch is arranged to operate on the reverse drive principle and hence the wipers are not stepped until the magnet is deenergised.

The operation of the mechanical impulse repeater to receive and transmit the dialled impulses is described in detail in the British patent referred to above. and the following brief description is given in order that the operation of the repeater in conjunction with the control relays and the selector repeater may be fully understood.

When the impulses energise the receiving magnet R, the off-normal contacts N of the mechanical impulse repeater are closed to prepare the circuit for relay BY, which circuit is maintained open at interrupter contacts Mdm of the marking magnet M which is maintained energised throughout the reception of the impulse series. In addition at contact i123 relay 1? completes a circuit for relay IS over; earth, contact i733, lower winding of relay IS, contact zb4, winding of the transmitting magnet S to battery. Relay IS operates over this circuit but the magnet S does not, Relay IS at contact is3 short-circuits its upper winding so that it is rendered slow to release. Relays ]J? and IS now remain operated until the end of the impulse series when relay C in the selector repeater releases and at contact 03 opens the circuit for relay IC. Relay 10 at contact 2'03 opens the circuit of the marking magnet M which releases and at interrupter springs Mdm closes a circuit for BY. Relay BY at contact byl prepares a further guarding circuit for the repeater and at contact bg E short-circuits relay IP from earth at the off-normal contacts N over the displaceable pin Z and reset pin Y. In addition at contact Z7113 relay BY locks up independently of the interrupter contacts Mdm. Relay IP releases after a short period and at contact ip2 opens the circuit of magnet CSM to permit the wiper of the control switch to advance its Wiper one step and at contact i113 opens the circuit for relay IS which also releases after a short period whereupon a circuit is closed for the transmitting magnet S over: earth, contacts 2793, b114, 2's3 winding of magnet S to battery. The sending magnet S now operates and opens its interrupter contacts Sdm whereupon relay 1P again energises and opens the circuit of the magnet S at contact i723. The impulses stored in the mechanical impulse repeater are now retransmitted over the impulse springs IPS.

It will be understood .of course that the magnet S should only be operated for a short period and that the operation of relays IP and IS are for the purpose of providing a delay between the reception and retransmission of the impulse series.

It is also to be noted that the control switch CS makes one step for each impulse series for a purpose which will be explained later in the description.

Returning now to the operation of the selector repeater, relay E operates on the first vertical step over: earth contacts bi, c2, ha5, interrupter contacts rm, ofi? normal contacts N2, winding of relay E to battery. Relay E at contact e! prepares a point in the energising circuit for the rotary magnet RM and at contact e2 closes a holding circuit for itself independent of relay C. When relay C releases at the end of the first impulses series it closes the circuit for the rotary magnet as follows: earth, contact bl, spring controlled by armature 02, contact cl, winding of rotary magnet RM to battery. The rotary magnet now energises and rotates the wipers (not shown) on to the first bank contact. In addition at contact rm the rotary magnet opens the locking circuit for relay E which now releases and at contact 6! opens the circuit for the rotary magnet which also releases.

If the line on which the wipers are now set is busy, earth potential will be present on the P conductor and the following circuit is again closed for relay E: earth on the P conductor, contact hail, interrupter contact rm, ofi normal contact N2 winding of relay E to battery. Relay E again operates and closes the circuit for the rotary magnet and this interaction between the relay and the magnet continues until an idle line is found. An idle line will have no potential aplied to the P conductor so that no earth will be present to relay E.

However the following circuit is now efiective: earth. contact bl, 11th step springs S2, winding of relay HA, interrupter contacts rm, vertical ofi normal contact N2, winding of relay E to battery.

Relay HA only, operates over this circuit which was not effective previously since relay HA was shunted and at contacts hal and M12 extends the connection to the next switch; at contact haS extends earth on the P conductor back to the preceding switches; at contact had opens the circuit for relay E and at contact hat opens the original energising circuit for relay E and at contact hat opens the short-circuit around contact M15.

The above series ofoperations take place on any call whether for a local subscriber or for a distant subscriber. Discrimination between the two types of call is, however, eifected by the level to which the selector repeater is raised in response to the first series of impulses. As pointed out above certain of the first 8 levels are allocated to local connections and the 9th and 10th levels are allocated to distant connections. When the selector repeater is raised to the 9th or 10th levels normal post springs NH and NP3 are opened while NPZ is closed. On the levels over which local connections may be set up normal post springs NPi and N1 3 remain closed whil spring NP2 remains open and hence on levels other than the 9th or 10th 1. e. on local calls, the locking circuit for relay HE is opened on the first rotary step of the selector repeater at rotary olf normal contacts NEE. Relay I-IB, therefore, de-energises and at contacts hbl and hbll disconnects the outgoing conductors of the selector repeater from the impulsing conductors leading from the mechanical impulse repeater and connects them to the loop extending from the calling subscriber.

At contact hbd relay HB opens the impulsing circuit to the mechanical impulse repeater and at contact hbt opens a further point in the circuit of relay IC. The mechanical impulse repeater is therefore released. Further on the first rotary step off-normal springs NR3 are closed and a circuit is completed for the release magnet Z from earth at normal post springs NPt whereupon the wipers of the selector repeater are restored to normal. The remaining impulses reset the selector repeater to a level at which openings NP! and NP3 are opened and control the setting of the local switches in the usual way, the impulses being repeated at contact a2.

If however the call is for a distant exchange normal post springs NP?! are operated and the locking circuit of relay HB now extends from earth, at contact hht over the normal post springs NP2. In addition normal post springs NP! operate to remove earth from the metering conductor since on a call to another exchange the charge will be assessed separately.

It is now necessary to consider the difference in operation of the circuit when the call to exchange B is made over a direct junction and when it is made over the intermediate exchange C. For this purpose it should be explained that for connections between exchange A and exchange B four digits are necessary, the first of which is always 0 and the remaining three are employed for setting the penultimate and final selectors in exchange B.

. Assuming first that the selector repeater seizes a direct junction to exchange B then this seizure takes place before the mechanical impulse repeater commences to retransmit the first digit 0, the necessary delay being caused by the release of relays IP and IS as described above. When however the first digit is retransmitted at the impulse springs IPS it is rendered ineffective in this case since these springs are short circuited by contact dad of relay DA.

relay DA. Relay DA now operates and removes the short-circuit from around the impulsing springs and connects them to the outgoing conductors of the selector repeater. The second, third and fourth digits registered on the mechanical impulse repeater are therefore retransmitted to set the switches in exchange B. When the four digits have been retransmitted the control switch steps to contact 6 whereupon earth is extended over contact hbl to shunt relay HB. Relay l-IB thereupon releases with the same results as described above.

The junctions extending from exchange A to exchange C over which a call to exchange B is set up, when all the direct junctions are unavailable, have their connections reversed in the banks of the selector repeater and hence as soon as one of these junctions is seized, relay DA operates with the same result as described above but in this case it operates before retransmission of any of the stored digits has taken place. All the four impulses stored in the mechanical impulse repeater are therefore retransmitted and the first digit 0 serves to position the incoming selector IS in exchange C to the 10th level over which it has access to junctions leading to exchange B. The mechanical impulse repeater is released after the retransmission of all the stored digits in the manner described above.

When the calling party replaces his receiver relay A releases, followed by relay B and a circuit is then closed for the release magnet ZM as follows: earth, contacts at, b3, vertical off-normal contact N3, winding of release magnet ZM to battery. Relay HA also releases and the selector repeater is therefore restored to normal.

A call from exchange A to exchange C will be set up in a similar manner to a call to exchange B over the preferred route except that in this case the first digit dialled is 9 instead of O. The operation of the system however is in general so similar in the two casesthat no further description will be given. It will of course be understood that alternative routing facilities can also be applied to cases where the direct jmictions between exchanges A and C are unavailable. In this case the alternative route would extend through exchange B.

It will be understood that with a larger system it may be necessary to provide the selector repeater with two sets of wipers, local connections being set up over one set and distant connections over the other. The connection of the wipers would be controlled by a wiper switching relay in accordance with the first digit and. the switch would also retain the drop-back feature.

I claim:

1. In an automatic telephone system, a selector switch, a plurality of mechanical impulse repeaters, means individual to said switch effective when operated for automatically connecting an idle one of said mechanical repeaters to said selector, means in said switch operated responsive to the seizure thereof by a calling subscriber for operating said first mentioned means, means in said switch operated responsive to the operative association of an idle one of said repeaters with said switch for signalling the calling subscriber, and means in said switch for controlling the setting of said switch in accordance with only the series of impulses of a first digit received from a calling subscriber and for setting said repeater in accordance with the series of impulses of all the digits received from a calling subscriber.

2. In an automatic telephone system, a selector. switch, a plurality of mechanical impulse repeaters, means individual to said switch effective when operated for automatically connecting an idle one of said mechanical repeaters to said selector, means in said switch operated responsive to the seizure thereof by a calling subscriber for oper ating said first mentioned means, means in said switch operated responsive to the operative association of an idle one of said repeaters with said switch for signalling the calling subscriber, and means in said switch for simultaneously controlling the setting of said switch and the setting of said repeater in accordance with the series of impulses comprising the first digit dialled by a calling subscriber and for thereafter controlling the setting of said repeater in accordance with the series of impulses comprising each of the remaining digits dialled by a calling subscriber.

3. In an automatic telephone system, a selector switch, a mechanical impulse repeater associated therewith, means in said switch operated responsive to received series of impulses from a calling subscriber corresponding to the digits of a called subscribers number, said selector switch operated to a certain position under control of said means in accordance with the series of impulses of a certain first digit, said repeater operated by said means in accordance with the series of impulses of all digits to register the same, means in said switch operated responsive to the positioning of said switch to said certain position for controlling said impulse repeater to cause the same to retransmit all the registered digits, and means in the repeater for rendering inefiective only the retransmitted series of impulses of the first registered digit.

4. In an automatic telephone system a first exchange, a mechanical impulse repeater at said second exchange, a selector switch at said exchange, a second exchange, trunk lines terminating in said second exchange accessible to said switch, a third exchange, preferred trunks terminating in said third exchange accessible to said switch, trunk lines interconnecting said second and said third exchange, means in said switch operated responsive to the seizure thereof by a calling subscriber and controlled by the series of impulses of each digit of a called number dialled by the calling subscriber, said means controlling said switch to select an idle preferred trunk line when the first digit dialled indicates that the called subscriber is located in said third exchange and controlling said impulse repeater to register all the digits of the called number, means in said switch effective when all of said preferred trunk lines are busy for causing said switch to select an idle trunk line to said second exchange, and means in said repeater operated responsive to the selection of an idle trunk line to said second exchange for controlling said repeater to retransmit series of impulses corresponding to all of the digits registered over said selected trunk line to said second exchange, means in said second exchange controlled by the impulses of the first digit retransmitted for selecting an idle trunk line interconnecting said second and said third exchanges, and switches at said third exchange controlled by the remaining retransmitted digits of the called number for connecting with the called subscriber.

5. In an automatic telephone system a first exchange, a selector and an impulse register at said first exchange, switching equipment at a second exchange, trunk lines extending to said second exchange, means in said switch controlled responsive to the reception of series of impulses corresponding to the digits of a called subscribers number transmitted by a calling subscriber for controlling said impulse register to thereby register all of said series of impulses, means in said switch operated by the series of impulses of the first digit for controlling the said switch to select an idle trunk line to said second exchange, means in said register operated responsive to the selection of an idle trunk line for rendering said register effective to retransmit all of the registered series of impulses over the selected trunk line, and means in said register for preventing the retransmitted series of impulses corresponding to the first digit from being transmitted over the selected trunk line and for permitting the remaining series of impulses corresponding to the remaining digits of the called number to be retransmitted over the trunk line, said remaining series of impulses controlling said switching equipment over said selected trunk line to complete a connection between a calling subscriber and a called subscriber.

6. In a telephone system, a first and a second exchange, a first group of trunk lines over which connections are completed between said exchanges, a second group of trunk lines over which connections are completed between said exchanges by way of a tandem exchange, a selector switch and an impulse register in said first exchange, a calling subscriber in said first exchange, means in said switch operated by impulses comprising a first digit dialled by said subscriber for controlling said switch to select an idle trunk line in said first group or said second group and for simultaneously controlling said register to register the impulses of the first digit, said means thereafter controlling said register to register the series of impulses corresponding to the remaining digits dialled by said subscriber, means in said register operated responsive to the seizure of an idle trunk line in either of said group for causing said register to start retransmitting impulses corresponding to the registered digits, and means in the register operated when the seized idle trunk line is in said first group for preventing retransmission of a first registered digit and permitting retransmission of remaining registered digits over said seized trunk line, said last mentioned means rendered ineffective when the seized idle trunk line is in said second group to permit the retransmission of all registered digits over said seized trunk line.

7. In an automatic telephone system, a selector switch, an impulse register, means for seizing said register to connect the same to said selector operated responsive to seizure of said selector by a calling subscriber, means for operating said selector responsive to first digits of called numbers to extend either local or outgoing calls and for operating said register to register said first digits, means in said switch operated when the first digit represents a local call for restoring the switch to normal and for disconnecting said register, means in said switch operated when the first digit represents a toll call for preventing said last mentioned means from becoming efiective and for controlling said register to retransmit the registered first digit.

8. In an automatic telephone system comprising a first and second exchange interconnected by trunk lines, a selector and an impulse register in said first exchange, means for simultaneously operating said selector and said register during the establishment of a connection to a called subscriber in either exchange, means for releasing said register when the call is for a subscriber in said first exchange and for preventing the release thereof when the call is for a subscriber in the second exchange, and means in said register effective when the call is for said second exchange for transmitting series of impulses over the interconnected trunk line to set the switching equipment in the second exchange.

9. In an automatic telephone system, a selector having directive primary movement and automatic secondary movement, a set of wipers positioned by said two movements, an impulse register,

an outgoing impulsing circuit for said register, means operated responsive to the seizure of said selector by a calling subscriber for operatively associating said register with said selector, means in said selector operated responsive to the operative association of said selector and said register for connecting said outgoing impulsing circuit to said set of wipers, means in said switch operated responsive to a first digit transmitted by a calling subscriber for controlling the directive primary movement and for controlling said register to register the said digit, said automatic secondary movement thereafter efiective to control .said wipers, and means in said register efiec tive upon the termination of the automatic secondary movement for controlling said outgoing impulse circuit to retransmit the registered digit over said set of wipers.

10. A telephone system as claimed in claim 3 wherein the impulses retransmitted by said repeater are transmitted over said selector switch.

11. A system as claimed in claim 3 wherein the mechanical impulse repeater is one of a plurality of such switches, and a rotary switch individual to said selector and controlled thereby is automatically controlled to search for and connect an idle one of said repeater to the selector when same is seized.

RUDOLPH FRANK STEHLIK. 

